U.S. patent number 4,130,622 [Application Number 05/854,161] was granted by the patent office on 1978-12-19 for method of making self-supporting tubular filter.
This patent grant is currently assigned to Abbott Laboratories. Invention is credited to Kenneth E. Pawlak.
United States Patent |
4,130,622 |
Pawlak |
December 19, 1978 |
Method of making self-supporting tubular filter
Abstract
A self-supporting tubular filter including a sleeve of filter
material and a frame formed by longitudinal and circumferential
ribs attached to the sleeve. The filter is characterized by a
longitudinal separation along a substantial length of the sleeve
which is spliced together by one of the longitudinal ribs. That rib
extends through the separation so that it overlies and is attached
to the interior and exterior surfaces of the sleeve adjacent to the
separation. Also disclosed are the use of the filter as a
microemboli blood filter and a method of its manufacture employing
a single male core pin with first and second female molds.
Inventors: |
Pawlak; Kenneth E. (Mundelein,
IL) |
Assignee: |
Abbott Laboratories (North
Chicago, IL)
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Family
ID: |
25090022 |
Appl.
No.: |
05/854,161 |
Filed: |
November 23, 1977 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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770890 |
Feb 22, 1977 |
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Current U.S.
Class: |
264/255;
210/497.01; 264/250; 264/266; 210/484; 264/DIG.48; 264/257 |
Current CPC
Class: |
B01D
29/111 (20130101); B29C 45/1418 (20130101); B29C
45/14344 (20130101); B01D 29/13 (20130101); B29C
45/1671 (20130101); Y10S 264/48 (20130101); B29C
2045/14983 (20130101) |
Current International
Class: |
B29C
45/14 (20060101); B29C 45/16 (20060101); B01D
29/11 (20060101); B29F 001/00 () |
Field of
Search: |
;264/247,255,257,266,DIG.48,250 ;210/483-485,497R |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Derrington; James H.
Attorney, Agent or Firm: Hardt; Aaron L. Niblack; Robert
L.
Parent Case Text
This is a division, of application Ser. No. 770,890, filed Feb. 22,
1977, now abandoned.
Claims
That which I claim is:
1. The process of making a self-supporting tubular filter
comprising the steps of:
(a) providing a sleeve of filter material having a longitudinal
line of weakness therealong,
(b) providing a core pin having outer dimensions slightly less than
the inner dimensions of said sleeve and including a longitudinal
channel therealong,
(c) inserting said core pin into said sleeve with said longitudinal
line of weakness aligned above said channel,
(d) providing a first female mold having a cavity complementary to
said ensleeved pin, said cavity including a longitudinal groove
therealong,
(e) enclosing said ensleeved pin inside said first female mold with
said line of weakness, said channel and said groove in
alignment,
(f) injecting a thermoplastic material into said channel of said
core pin until said channel becomes filled and said injected
thermoplastic material forces outwardly against said sleeve at said
longitudinal line of weakness separating said sleeve thereat and
filling said groove of said female mold,
(g) allowing said thermoplastic material to solidify while in
contact with said separated sleeve so that said solidified material
in said filled channel and groove form an integral rib splicing
said sleeve, said rib being attached to the internal surfaces of
said sleeve adjacent to said separation and extending through said
separation a predetermined distance external to said sleeve,
(h) removing said ensleeved core pin from said first female
mold,
(i) providing a second female mold having a cavity complementary to
said ensleeved pin, said second female mold cavity including a
longitudinal groove therealong having the capacity to receive said
portion of said rib external to said sleeve,
(j) enclosing said ensleeved pin inside said second female mold
with said portion of said rib external to said sleeve and said
groove of said second female mold cavity in alignment,
(k) injecting thermoplastic material into said groove of said
second female mold cavity until said groove is filled and allowing
said injected thermoplastic material to solidify so that it
overlies and attaches to the external surfaces of said sleeve
adjacent to said separation,
(l) removing said ensleeved pin from said second female mold;
and
(m) removing said sleeve from said core pin; whereby a
self-supporting tubular filter having an integral rib splicing a
longitudinal separation of said sleeve both internally and
externally is formed.
2. The process of making a self-supporting tubular filter as stated
in claim 1 wherein said sleeve is cylindrical.
3. The process of making a self-supporting tubular filter as stated
in claim 1 and further characterized in that said sleeve has two
diametrically opposed said longitudinal lines of weakness
therealong, said core pin has two diametrically opposed said
longitudinal channels therealong, said first and second female
molds each have two diametrically opposed said longitudinal grooves
therealong and said tubular filter has two said integral ribs
splicing said sleeve both internally and externally.
4. The process of making a self-supporting tubular filter as stated
in claim 3 wherein step (a) is achieved by superimposing two strips
of said filter material and heat-sealing said strips together along
two spaced-apart parallel paths.
5. The process of making a self-supporting tubular filter as stated
in claim 1 and further characterized in that said core pin, said
first female mold and said second female mold have frame-forming
recesses wherein said thermoplastic material can flow during steps
(f) and (k) and solidify during steps (g) and (k) to form a frame
of longitudinal and circumferential ribs about said sleeves.
Description
BACKGROUND OF THE INVENTION
The present invention relates to self-supporting tubular filters
and, particularly, filters useful for the filtration of blood. More
particularly, this invention relates to the manufacture of such a
filter having improved tear resistance when in use.
Self-supporting filter elements are known in the prior art. For
example, U.S. Pat. No. 3,408,438 granted Oct. 29, 1968 to R.
Staunton relates to a method of making self-supporting filter
elements from fibrous materials. While the filters of Staunton can
be formed into a belt or loop, they are essentially flat materials
joined by a suitable fastener after a flexible support has been
incorporated thereon. French Pat. No. 1,084,239 published Jan. 18,
1955 by M. Rene Jaume disclosed a method for making self-supporting
tubular filters and U.S. Pat. No. 3,746,595 granted July 17, 1973
to H. Leason discloses an improvement to the filter of Jaume.
Many materials having a porosity suitable for use as a filter
cannot be extruded or otherwise molded as an integral tube. Thus,
as illustrated by the patents of Staunton, Jaume and Leason, such
materials are formed into tubes by joining flat sheets of the
material end to end upon themselves or by sealing two flat sheets
to each other along their respective longitudinal edges. No matter
how such a tube is formed, its longitudinal seam constitutes a line
of weakness likely to rupture when exposed to substantial
pressures. If such a tube is in use in a filter when its seam
ruptures, it is likely that the integrity of the filter will be
lost and that fluid passing therethrough will pass through the
rupture in the tube without being filtered.
While such a loss of integrity is undesirable in any filtration
process, its occurrence in a blood filter could be disastrous and,
therefore, a highly reliable sealing of the seam is a necessity.
Unfortunately, in those instances, such as blood filtration,
wherein the pore size of the filter material and the material
molded thereon generally prevent the formation of a mechanical lock
or seal being formed between the filter material and the ribs
molded to it.
Accordingly, a need exists for a tubular filter that, during its
intended use, will not rupture along seam therein resulting from
its formation.
SUMMARY OF THE INVENTION
The primary object of the present invention, therefore, is to
provide an improved self-supporting tubular filter which will be
free from the aforementioned and other disadvantages of prior
devices of this type. More particularly, it is an object of the
present invention to provide a self-supporting tubular filter that
has improved resistance to rupture or tear when exposed to the
fluid pressures of its intended use. Still another object is to
provide such an improved filter that is suitable for use as a
microemboli blood filter.
In accordance with these and other objects, there is provided by
the present invention a self-supporting tubular filter including a
sleeve of filter material and a frame formed by longitudinal and
circumferential ribs attached to the sleeve. A seam of the sleeve
is caused to separate along a substantial length thereof during
manufacture of the filter and the sleeve is spliced together by one
of the longitudinal ribs which extends through the separation so
that it overlies and is attached to the interior and exterior
surfaces of the sleeve adjacent to the separation. Where the sleeve
has more than one seam, each seam may be separated during
manufacture and each separation spliced together by one of the
longitudinal ribs.
Preferably, the self-supporting tubular filter is manufactured by
joining the longitudinal edges of one or more flat strips of filter
material to form a sleeve. The sleeve is placed over an injection
molding core pin having a longitudinal channel which is aligned
with a seam of the sleeve. The ensleeved core pin is then placed in
a first female mold having a cavity complementary to the ensleeved
core pin and including a longitudinal groove situated in alignment
with the longitudinal channel of the core pin and longitudinal seam
of the sleeve.
A thermoplastic material is then injected into the channel of the
core pin until the channel becomes filled and causes the sleeve to
separate along a substantial length of its seam. The thermoplastic
then enters the longitudinal groove of the first female mold and is
allowed to solidify in the channel and groove to form an integral
longitudinal rib splicing the sleeve and attached to the internal
surface of the sleeve adjacent to the separation. Preferably, the
groove in the female mold is substantially V-shaped at its bottom,
so that the portion of the integral rib external to the sleeve
forms substantially a prism.
The ensleeved core pin is then removed from the first female mold
and placed into a second female mold having a cavity complementary
to the ensleeved core pin and including a longitudinal groove
capable of receiving the external portion of the integral rib
splicing the sleeve at its separated seam. Thermoplastic material
is then injected into the groove of the second female mold and
allowed to solidify while in contact with the exterior portion of
the integral rib and the exterior surfaces of the sleeve adjacent
to the separation. The ensleeved core pin is then removed from the
second female mold and next the sleeve with its attached frame
removed from the core pin.
Preferably, each seam of the sleeve will be separated and spliced
by a longitudinal rib, if the sleeve has more than one longitudinal
seam. Additional longitudinal and circumferential ribs are attached
to the filter by the use of additional channels or grooves in the
core pin and female molds. Preferably, each end of the sleeve is
secured by the circumferential ribs.
BRIEF DESCRIPTION OF THE DRAWING
Other objects and attendant advantages will become obvious to those
skilled in the art by reading the following detailed description in
connection with the accompanying drawing, wherein like reference
characters designate like or corresponding parts throughout the
several figures thereof and wherein:
FIG. 1 is a front elevational view of a preferred embodiment of the
self-supporting tubular filter of the present invention,
FIG. 2 is a top view thereof,
FIG. 3 is a cross-sectional view along the line 3--3 in FIG. 1 of
the filter thereof,
FIG. 3a is an enlarged view of the uppermost portion of FIG. 3,
FIG. 4 is a perspective view of an injection molding core pin
useful in the manufacture of the filter of FIG. 1,
FIG. 5 is a cross-sectional view of the core pin of FIG. 4
ensleeved by a filter material and inserted into a first female
mold useful in the manufacture of the filter of FIG. 1,
FIG. 6 is a cross-sectional view of the core pin of FIG. 4 after
the molding step illustrated in FIG. 5; and,
FIG. 7 is a cross-sectional view of the core pin and attachments
shown in FIG. 6 inserted into a second female mold useful in the
manufacture of the filter of FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
Referring to the drawing, there is shown in FIG. 1 a preferred
embodiment of a self-supporting tubular filter 9 manufactured in
accordance with the present invention. Filter 9 includes a sleeve
11 of filter material which has a frame of longitudinal ribs 15 and
circumferential ribs 13 attached to it.
The filter material of which sleeve 11 is made can be any woven,
nonwoven, or foamed material having suitable porosity for the fluid
desired to be filtered. For use in microemboli blood filtration the
material should have substantially all its pores greater than 5
microns and less than 170 microns in diameter. Preferred filter
materials are nylon or polyester.
The frame of filter 9 can be made of any suitable thermoplastic
material, whether rigid or flexible. Preferred rigid materials are
ABS copolymers (acrylonitrile, butadiene and styrene),
cellulose-propionate, polycarbonate, nylon; or acrylic,
glass-filled acetal resins, while polypropylene is preferred for
flexible frames.
Viewed from its top, as in FIG. 2, longitudinal ribs 15 of filter 9
can be seen both inside and outside of sleeve 11. As illustrated in
FIG. 3, at least one of the longitudinal ribs is an integral rib
15' extending through a separation 21 in sleeve 11 so that it
overlies and is attached to the interior and exterior surfaces of
sleeve 11 adjacent to the separation 21. Preferably, filter 9 has
one such rib 15' for each longitudinal seam present in sleeve 11 as
a result of its formation.
The self-supporting tubular filter 9 of this invention is
manufactured by a two-step injection molding process. Sleeve 11 is
formed of a suitable filter material by joining the longitudinal
edges of one or more sheets together into a tube. Preferably, the
sheets are joined by heat sealing the edges together of two
superimposed sheets to form a cylindrical tube having diametrically
opposed seams. The longitudinal seam along which the edges are
joined results in a line of weakness in sleeve 11.
An injection molding core pin 31, as illustrated in FIG. 4, is then
inserted into sleeve 11 in a manner such that a seam of sleeve 11
lies over and in alignment with a longitudinal channel 33 of core
pin 31. Preferably, filter 9 will be cylindrical and when it is,
core pin 31 will also be cylindrical. The outer dimensions of core
pin 31 are slightly less than the inner dimensions of sleeve 11 to
allow the core pin to be readily inserted therein and for other
molding considerations.
Core pin 31 ensleeved by sleeve 11 is then inserted into a first
female two-part mold shown generally as 41 in FIG. 5. Mold 41 has a
cavity 43 complementary to the ensleeved core pin 31 that when
closed allows no movement of sleeve 11 on core pin 31. Cavity 43
has a longitudinal groove 45, which groove preferably extends the
entire length of sleeve 11 and has a V-shaped cross-section. When
the ensleeved core pin 31 is inserted in first female mold 41, the
line of weakness of sleeve 11, longitudinal channel 33 and
longitudinal groove 45 are in alignment.
Using technology well known in the art of injection molding, a
liquid thermoplastic material is then injected into channel 33 of
core pin 31 until channel 33 fills and forces sleeve 11 outwardly
in the vicinity of its seam. By careful matching of the respective
inner and outer dimensions of sleeve 11 and core pin 31, sleeve 11
will separate along a substantial length of its seam and the edges
of sleeve 11 at the separation will be forced against the sides of
groove 45 as the thermoplastic material enters and fills groove 45.
Preferably, sleeve 11 is caused to separate along its entire
length. The thermoplastic material is then allowed to solidify so
that an integral rib 15' is formed splicing sleeve 11 by its
attachment to the internal surfaces of the sleeve adjacent to the
separation and extending through the separation a predetermined
distance external to the sleeve.
Core pin 31 ensleeved by sleeve 11 and the attached rib 15' is then
removed from the first female mold 41. When core pin 31 has a
plurality of longitudinal channels 33, as shown in FIGS. 4 and 5,
sleeve 11 will now have a plurality of longitudinal ribs attached
to its interior surface, as illustrated in FIG. 6. Further, if
desired, by means of suitably positioned circumferential channels
on core pin 31 and/or mold 41, sleeve 11 may now have a plurality
of circumferential ribs 13 attached to its ends.
While still inserted in sleeve 11, core pin 31 is then enclosed
inside a second female two-part mold 51, as generally shown in FIG.
7. Mold 51 has a cavity 53 complementary to the ensleeved core pin
31 and its attached rib 15' and a longitudinal groove 55 having the
capacity to receive the portion of rib 15' external to sleeve 11.
In the preferred embodiment, mold 51 has a plurality of grooves 55
and may also have circumferential grooves in cavity 53, if
desired.
With the external portion of rib 15' of sleeve 11 and a groove 55
in alignment, by techniques well known in the art of injection
molding, a liquid thermoplastic material is injected into the
groove 55 until filled and then allowed to solidify so that it
overlies and attaches to the external surfaces of sleeve 11
adjacent to separation 21. When the first mold 41 has a groove 45
of the preferred V-shape, the external portion of rib 15' will form
an elongated prism that will readily melt when contacted by the
liquid thermoplastic injected into the second female mold 51. Thus,
when the thermoplastic solidifies, rib 15' will be integral and
substantially monostratum. When ensleeved core pin 31 is removed
from mold 51 and core pin 31 removed from sleeve 11 and its
attached longitudinal and circumferential ribs, the self-supporting
tubular filter 9 of this invention will be formed.
While FIG. 1 illustrates the preferred embodiment of filter 9, it
will be readily apparent to those skilled in the art that many
other configurations of frames may be attached to a sleeve 11
within the spirit and scope of this invention. Further, it will
likewise be obvious to those skilled in the art that the filters of
this invention can be manufactured by various equivalent
methods.
* * * * *